This dissertation outlines the development of several laser-based methods of detecting chemicals at a distance. They are based on two forms of coherent Raman scattering: coherent anti-Stokes Raman scattering and stimulated Raman scattering. The specific motivation is to detect trace quantities of explosives, but the techniques can be adapted to other applications where chemical analysis of macroscopic samples is of interest. Each method is developed toward an imaging modality as the ultimate demonstration of sensitivity and specificity. Spontaneous Raman scattering is a linear process sensitive to molecular vibrations and well known for its chemical specificity. Unfortunately, this weak signal is only suitable for standoff detection of chemicals in bulk form. Coherent Raman processes are non-linear phenomenon in which the phase of the scattered light can be predicted or controlled. This can lead to dramatic enhancements in the signal strength through coherent addition of the fields from different scatterers and allows amplification through externally applied fields. These phenomena are utilized in the development of the most powerful Raman-based standoff detection systems to date, capable of detecting nanogram quantities of explosives with a few laser shots at 10 meters. The technique is non-destructive, using laser wavelengths in the near IR with an average power of less than 10 mW. -- Abstract.
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